In the Linux kernel, the following vulnerability has been resolved:
LoongArch: Fix missing dirty page tracking in {pte,pmd}_wrprotect()
When hardware page table walker (PTW) is enabled on LoongArch, the CPU
may set _PAGE_DIRTY directly in the page table entry during a write TLB
miss, without going through the software TLB store handler. The software
TLB store handler (tlbex.S:254) sets both _PAGE_DIRTY and_PAGE_MODIFIED
together:
ori t0, t0, (_PAGE_VALID | _PAGE_DIRTY | _PAGE_MODIFIED)
Since hardware PTW only sets _PAGE_DIRTY, the software-only bit, i.e.
_PAGE_MODIFIED is left unchanged. This creates a window where a PTE has
_PAGE_DIRTY set (hardware knows the page is dirty) but _PAGE_MODIFIED
clear (software is unaware).
When fork()/clone() triggers copy-on-write, __copy_present_ptes() calls
pte_wrprotect(), which unconditionally clears both the _PAGE_WRITE and
_PAGE_DIRTY bits:
pte_val(pte) &= ~(_PAGE_WRITE | _PAGE_DIRTY);
Since _PAGE_MODIFIED was never set, the dirtiness information is lost
completely. Subsequently, when memory pressure triggers page reclaim,
page_mkclean() / try_to_unmap() sees the page as clean (i.e. pte_dirty()
returns false) and the page may be freed without writeback, causing data
corruption.
Fix this by propagating the _PAGE_DIRTY bit to the _PAGE_MODIFIED bit in
both pte_wrprotect() and pmd_wrprotect() before clearing writeable bits:
if (pte_val(pte) & _PAGE_DIRTY)
pte_val(pte) |= _PAGE_MODIFIED;
The pmd_wrprotect() fix handles the CONFIG_TRANSPARENT_HUGEPAGE case,
where pmd entries need the same treatment.
This ensures the software dirty tracking bit (checked by pte_dirty() and
pmd_dirty(), which read both the _PAGE_DIRTY and _PAGE_MODIFIED bits) is
preserved across fork COW write-protection.
The issue was found by the LTP madvise09 test case, which exercises page
reclaim after "madvise(MADV_FREE), write and fork" operation sequence on
private anonymous mappings.
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (7.1): severity, escalated by confirmed exploitation. This CVE's 7.1 is its impact severity (EG Severity), not escalated.
- EG Severity
- 7.1 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-17). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines.
Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it